Exam Questions

Question 1

Explain how the monkeypox virus is able to replicate in humans.

(3 marks)

Answer 1

• The virus binds to a molecule on the surface of the skin cell (1)
• The viral DNA enters the cell (1) and use the host skin cell’s ribosomes/organelles to replicate in the skin cells (1)

Question 2

Explain why smallpox vaccine is not recommended for people at risk of HIV/AIDS.

(3 marks)

Answer 2

• HIV/AIDS is an immunodeficiency syndrome that causes a reduction in T-helper cells (1)
• This affects the immune system’s ability to activate cytotoxic T cells and B cells (1)
• The patient would be unable to control the live virus vaccine and would therefore be susceptible to a smallpox infection (1)

Question 3

Explain how monkeypox could have emerged into the human population.

(3 marks)

Answer 3

• Monkeypox existed in a monkey population (1)
• Close contact between humans and monkeys allowed the virus to pass from monkeys to humans (1)
• The virus mutated to live more easily in humans (1)

Question 4

Discuss three factors that affect the movement of DNA fragments through the agarose gel during gel electrophoresis.

(3 marks)

Answer 4

• The size of the DNA fragments as smaller fragments will move further (1)
• The viscosity of the agarose gel because a thicker gel will make fragments move slower (1)
• The voltage applied as higher voltage causes DNA to travel faster through the gel (1)

NOTE: Voltages that are too high can possibly melt the gel or cause smearing or distortion of DNA bands.

Question 5

Self-tolerance refers to the ability of the immune system to not mount a response against its own cells. Describe the consequence if self-tolerance does not occur.

(2 marks)

Answer 5

• If self-tolerance does not occur, then the immune system will detect self as non-self and start to destroy tissues within an individual’s own body (1)
• This may result in an autoimmune disease (1)

Question 6

Design an experiment (tailored to question).

(5 marks)

Answer 6

• Independent variable
• Dependent variable
• Controlled variables
• Control group
• Sample size

NOTE: The control group is used to compare the effect of the independent variable.

Question 7

A study examined the effect of increased temperatures on the weight and wing lengths of birds. The validity of the study was enhanced by gathering data from non-migratory birds.

Explain the benefit of using non-migratory birds with reference to the impact of the gene pool on the population of birds studied.

(3 marks)

Answer 7

• The non-migratory birds function as a control group to compare against other data, making a valid experiment (1)
• There would be limited gene flow between populations of birds (1)
• The gene pool would have changed due to mutations, not gene flow, over the duration of study (1)

Question 8

The proteome in prokaryotes compared to the genome is…

(MC)

Answer 8

• Equal to the genome of any genetic material in prokaryotes
• Because prokaryotes are more simplistic

Question 9

Explain why biofuel is more environmentally friendly than fossil fuels.

(3 Marks)

Answer 9

• Biofuels are renewable, whereas fossil fuels are non-renewable (1)
• Biofuels are (theoretically) carbon-neutral, whereas fossil fuels are not carbon-neutral (1)
• Biofuels recycle waste from industries such as farming, whereas fossil fuels are derived from raw materials (1)

NOTE: To be carbon-neutral is to emit and absorb the same amount of carbon dioxide from the atmosphere.

Question 10

What ethical response would be expected from researchers if they discovered that recombinant human insulin was significantly more effective than insulin from cows or pigs?

(3 Marks)

Answer 10

• Researchers should stop the clinical trial and people who are being given the animal insulin should be offered the more effective recombinant version of the insulin (1)
• Stop production of insulin from animals to protect their welfare (1)
• Release information to the public to increase informed decision (1)

Question 11

Explain the benefit of having two doses of a vaccine instead of one.

(2 Marks)

Answer 11

• The first dose leads to the activation of B cells and the development of a small number of memory cells (1)
• The second dose increases the number of memory cells for a more rapid response upon reinfection and greater antibody production (1)

Question 12

The process of bacterial transformation.

(MC)

Answer 12

• DNA of interest and plasmid are incubated with an endonuclease
• DNA of interest and plasmid are incubated with DNA ligase
• Recombinant plasmid is formed
• Bacteria are heat shocked to increase plasmid uptake
• Bacteria are placed on an agar plate with an antibiotic to determine transformation

Question 13

Chronic inflammation caused by Mycobacterium tuberculosis can form granulomas, which consist of nectrotic cells and leukocyte clusters in the lungs.

The granulomas would form because of…

(MC)

Answer 13

• Chemotaxis of innate immune cells to the site of infection from release of cytokines

Question 14

Myogloboin is a biological macromolecule that assists in the transport of oxygen in muscle. It is composed of 153 amino acids from 10 000 bases in the DNA.

The difference in numbers can be accounted for through…

(MC)

Answer 14

• RNA processing with exon retention and intron removal

Question 15

African swine fever is a contagious viral disease in pigs that can spread rapidly, creating an epidemic.
The appropriate detection technique to identify an infection with this specific type of virus is…

(MC)

Answer 15

• Polymerase chain reaction

NOTE: Viruses cannot grow on agar plates. Viruses are too small to be viewed under a microscope. Morphological identification would not work as viruses have the same basic structure of a protein coat (only differ through protein receptors on the surface).

Question 16

The Denisovans interbred with population of Homo sapiens.

Explain why some paleontologists may dispute the classification of these species.

(1 Mark)

Answer 16

• The definition of speciation is the inability to produce viable fertile offspring with other populations of different species
• The Denisovans, Neanderthals and Homo sapiens were still able to interbreed and produce viable offspring

Question 17

The trp operon is classified as a repressible system. Explain what this means.

(2 Marks)

Answer 17

• A repressible system refers to the system always being functional until the protein is not required by the cell (1)
• Tryptophan is synthesised by the cell until it is present in the bacteria’s environment – this is when the repressor protein is synthesised and binds to the operator region (1)

NOTE: Inducible systems are always inactive until the cell requires the protein.

Question 18

Outline how a selective breeding program could be carried out to produce populations of white spruce tree that are highly resistant to the budworm.

(3 Marks)

Answer 18

• Identify and breed trees that show the highest degree of resistance to the budworm (1)
• Choose offspring with the most resistance to the budworm as parents of the next generation of trees (1)
• Continue this process over many generations (1)

Question 19

The use of CRISPR-Cas9 may result in off-target modifications.

What are off-target modification and why would they be a matter of concern to scientists?

(2 Marks)

Answer 19

• An off-target modification occurs when Cas9 cuts at unintended locations in the genome (1)
• Off-target modifications are a matter of concern because if the sequence of another gene is interrupted, then the expression of that gene may be prevented (1)

Question 20

CRISPR-based systems fundamentally changed the field of genetic engineering because “they allow for genomes to be edited in living organisms cheaply, with ease and with extreme precision.”

Explain how CRISPR-based systems can be used with ease and extreme precision.

(2 Marks)

Answer 20

• The use of tailor-made sgRNA to guide Cas9 to its specific target site improves the precision of gene editing (1)
• CRISPR technology improves the ability to carry out genetic modification as it can be used to add desirable DNA into a genome, remove undesirable sequences or modify mutations in order to correct a DNA sequence (1)

Question 21

Explain how there can be over 300 monomers in a single RNA molecule but only 10 amino acids translated.

(2 Marks)

Answer 21

• Many monomers make up introns, which do not code for amino acids (1)
• Each amino acid is coded for by three monomers (1)

Question 22

A higher concentration of oxygen is found in the stroma when a plant is photosynthesising compared to when it is not.

Explain the difference in oxygen concentration in the stroma.

(2 Marks)

Answer 22

• Water is split in the light-dependent reaction to produce oxygen gas (1)
• Oxygen produced during photosynthesis diffuses into the stroma (1)

Question 23

Explain if it could be possible to develop against a vaccine against allergens.

(2 Marks)

Answer 23

• It would not be possible (1)
• A vaccine would lead to greater production of antibodies, which would in turn increase the allergic response (1)

Question 24

Explain why antibody tests cannot identify the difference between the antibodies produced by different viruses.

(2 Marks)

Answer 24

• The shape of viruses’ antigens are similar, enabling them to bind to the same antibody (1)
• The viruses bind to the antigen-binding site of the antibody (1)

Question 25

Aedes mosquitoes are not found on every continent. They cannot fly great distances. Vaccines are currently being trialled for the Zika virus.

Describe three different approaches, other than vaccination, that government health officials can use to reduce the spread of the Zika virus.

(3 Marks)

Answer 25

• Mandating quarantine for people who come from countries in which the disease occurs (1)
• Using mosquito nets or fly screens on windows (1)
• Creating education campaigns about suitable clothing and use of insect repellent (1)

Question 26

A new treatment for some cancers includes the use of conjugated monoclonal antibodies, which have an anti-cancer drug attached.

The main advantage of using conjugated monoclonal antibodies in this new cancer treatment is that they…

(MC)

Answer 26

• Reduce the effects of the anti-cancer drug on non-cancerous cells

Question 27

Explain why antigenic shift is of concern for scientists.

(2 Marks)

Answer 27

• Antigenic shift generates a new virus that has not been previously exposed to humans, hence, no immunity (1)
• Scientists need time to produce a new vaccine for the new strain (1)

Question 28

Hemolytic disease of the newborn (HDN) can occur if a Rhesus-negative mother is pregnant with a Rhesus-positive fetus. During pregnancy and birth, some fetal blood cells may enter the mother’s bloodstream. The mother makes antibodies against the fetal RhD antigens. This is usually not a problem until there is a second pregnancy with a Rhesus-positive fetus. RhD antibodies made by the mother then
cross the placenta, resulting in the possible death of the newborn.

Explain, by referring to the immune response, why the fetus in a second pregnancy is at far greater risk of HDN than the first Rhesus-positive fetus.

(2 Marks)

Answer 28

• B memory cells produced during the first pregnancy (1) enables a larger and more rapid response during second pregnancy (1)

Question 29

Explain why making a correct identification of a viral pathogen is important in the control of a disease.

(3 Marks)

Answer 29

• Identify pathogen and isolate antigens (1). This would enable the production of a vaccine with complementary shape (1). Administering this vaccine reduces the number of susceptible hosts, preventing the transmission of the disease (1).
• OR
• Specific pathogens have specific methods of transfer (1). They may require specific methods of control such as a particular antiviral drug (1). Incorrect identification can lead to continued infections and spread (1).

Question 30

Give an example of a type of protein within a yeast cell that may change in concentration. Explain why this change is necessary.

(3 Marks)

Answer 30

• Enzyme (1)
• If there is a change in substrate concentration (1), then more or less enzyme may be produced to conserve ATP (1)

Question 31

Explain why the uptake of glucose into cells can be used to measure the metabolic activity of cells.

(2 Marks)

Answer 31

• Glucose is an input for cellular respiration (1)
• The ATP produced from glucose is used for metabolism (1)

NOTE: Metabolism refers to the chemical processes that occur within a living organism in order to maintain life.

Question 32

Viral RNA must be converted to DNA before PCR can occur. The process by which this occurs is called reverse transcription PCR (RT-PCR).

State two reasons why virus identification using RT-PCR cannot be used for all viruses.

(2 Marks)

Answer 32

• A suitable or complementary probe may not be available (1)
• Not all viruses are made of RNA (1)

NOTE: Probes attach to complementary sequences that are only found in particular viruses.

Question 33

Explain how scientists design sgRNA molecules and outline the function of sgRNA in gene editing.

(2 Marks)

Answer 33

• Scientists identify a gene that acts as a template and create a complementary sgRNA strand that binds with Cas9 (1)
• sgRNA then guides Cas9 to the target gene (1)

Question 34

Describe two types of evidence that would allow biologists to classify a species as extinct on a particular island.

(2 Marks)

Answer 34

• No sightings or fossil remains of the species on the island (1)
• No other evidence such as DNA, feathers, nests or their common food source (1)

Question 35

Describe how the immune system of a person who has recently contracted COVID-19, would distinguish between cells that need to be destroyed and cells that do not need to be destroyed.

(2 Marks)

Answer 35

• Every nucleated cell has MHC-1 markers on their surface, allowing them to be recognised as self; these cells therefore do not activate the immune system (1)
• If a cell has a non-self antigen displayed on its surface (in the case of COVID-19, it is a viral fragment), then the immune system is activated (1)

Question 36

Homo erectus may have interbred at some point with the Denisovans. The Denisovans may have also interbred with modern humans in Indonesia and New Guinea as recently as 30 000 years ago. Much of the Denisovan genome has been sequenced, but the Homo erectus genome has not.

Based on the information provided, describe the evidence of this interbreeding that would be present in modern Southeast Asian human genomes.

(2 Marks)

Answer 36

• Since the Denisovan genome has been sequenced, some Denisovan DNA should be present in some Southeast Asian genomes. (1)
• Since the Homo erectus genome has not been sequenced, genome material of unknown origin should be present in some Southeast Asian genomes. These unknown segments could come from Homo erectus. (1)

Question 37

Explain how mutations in X (gene) allows for a specific phenotype in Y (species) to have evolved.

(4 Marks)

Answer 37

• Mutations occur randomly in X, creating variation in the ancestral species (1)
• Some mutations in X create a phenotype that provides the affected organism with a selective advantage in their environment (1)
• This organism is more likely to survive and reproduce, producing offspring with the same selective advantage (1)
• Over generations, the continued survival of this organism with the favourable phenotype leads to the modern species having the same phenotype (1)

NOTE: Answer must be tailored to question specifics.

Question 38

Describe evidence (other than DNA sequences and protein structures) scientists could use to help classify individuals into different species.

(2 Marks)

Answer 38

• Individuals within the same species would be able to breed, producing viable and fertile offspring (1)
• Anatomical features; individuals of the same species would have more characteristics in common with each other than with those of a different species (1)

Question 39

Single-celled algae from the coral reef are exposed to mutagens within a laboratory setting. Some of these algae are reintroduced back into the coral reefs.

What is a disadvantage of this approach?

(1 Mark)

Answer 39

• One of the following
• Introduction of the genetically modified individuals may have unexpected or unintended effects on the coral reef systems
• Cross breeding with wild species may cause the expression of detrimental characteristics
• Loss of variation

Question 40

Describe how constant inflammation could affect HIV patients.

(2 Marks)

Answer 40

• Constant inflammation would cause persistent pain, redness and heat, wasting energy that is needed to fight the HIV infection (1)
• Brings more lymphocytes and phagocytes to the inflamed area, preventing them from being used to fight infection elsewhere (1)

Question 41

Name the type of immunity that the joey obtains from the antibodies in the milk and explain how this form of immunity is beneficial to the joey.

(3 Marks)

Answer 41

• Natural passive immunity (1)
• Provides antibodies to fight disease (1)
• A joey’s immune system is underdeveloped and cannot produce antibodies quickly enough on its own or has no B-memory cells (1)

Question 42

Scientists tested the tammar wallaby milk peptides and found them to be 10 times more effective than antibiotics such as tetracycline and ampicillin, which are commonly used to fight human diseases.

Suggest what the scientists would hope to achieve as a result of further testing of these peptides with antibiotic properties.

(1 Mark)

Answer 42

• That it is safe for humans (1)
• These peptides could be used instead of antibiotics and used against resistant strains of bacteria that cause human diseases (1)

NOTE: Either answer would be accepted.

Question 43

State two ethical implications of the genetic screening of newborn babies.

(2 Marks)

Answer 43

• Privacy of the newborn baby
• Concerns about whether the data is secure

Question 44

Describe the role that autoantibodies play in causing the symptoms of an autoimmune disease.

(1 Mark)

Answer 44

• Autoantibodies attack self cells and the destruction of this tissue leads to symptoms of autoimmune disease (1)

Question 45

Describe the evidence that would need to be present in a 25 million year old fossil to support the evolution of Equus from Hyracotherium.

Answer 45

• The length of the middle bone would need to be between that of Mesohippus and Merychippus
• The width of the middle bone would need to be between that of Mesohippus and Merychippus
• The size of the hoof would need to be bigger than that of Mesohippus but smaller than Merychippus

Question 46

If the temperature of the bacterial cells was increased above the optimal temperature for cellular activity, would the activity of the proteins of the gene expression increase, decrease or stay the same? Justify your response.

(3 Marks)

Answer 46

• An increase in temperature would lead to decreased activity of the enzyme (1)
• The enzyme would eventually denature (1)
• Substrates no longer able to fit or bind to the active site of the enzymes (1)

Question 47

Scientists hope to design a molecule that will specifically inhibit HIV enzymes. Once this molecule has been created, they plan to test it on patients infected with HIV.

Identify four requirements or aspects of the experimental design that would need to be considered when the scientists are planning their trial of this molecule.

(4 Marks)

Answer 47

• Use a large number of HIV-positive participants (1)
• Give one experimental group the molecule and one control group no molecule (placebo) (1)
• Have appropriate control variables (for example, same gender, same duration of treatment, same sample volume of thymus tested for T helper cell count) (1)
• Repeat the trial to confirm reliability of results (1)

Question 48

Stem cells are undifferentiated cells that have the capacity to differentiate into a variety of specialised cells. For example, bone marrow stem cells can differentiate into lymphocytes (B and T), mast cells and macrophages.

Describe how regulatory genes could play a role in the specialisation of these types of cells.

(2 Marks)

Answer 48

• Regulatory genes may activate or deactivate more than 1 structural gene (or cluster of structural genes) (1)
• If different combinations of structural genes are activated by a regulatory gene, the structural proteins produced may change the type of cell that cell specialises into (1)

Question 49

A plasmid contains two antibiotic resistant genes: ampR and tetR. The tetR gene has a recognition site for one of the restriction enzymes inside it, while the ampR gene does not.

The plasmids are then mixed with bacteria, which are stimulated to take up the plasmids; however, not all of the bacterial cells will take up plasmids and, of those that do, not all of the plasmids will be recombinant plasmids. The bacteria that successfully take up the recombinant plasmids only will be resistant to…

(MC)

Answer 49

• Ampicillin but not to tetracycline
• The tetR gene would have been cut by a restriction enzyme
• The ampR gene is located away from the restriction site and is therefore unaffected

Question 50

Desired genes are mixed with plasmids, which are then incorporated into bacteria. It is important that these plasmids contain two antibiotic resistant genes; one located away from an EcoR1 restriction site and the other containing an EcoR1 restriction site within its sequence.

Describe the purpose of these two antibiotic resistant genes in identifying the successfully transformed bacteria.

(2 Marks)

Answer 50

• The antibiotic resistant gene located away from any recognition sites is used to identify the bacteria that have successfully taken up a plasmid. (When treated with the corresponding antibiotic, these bacteria will be unaffected). (1)
• The antibiotic resistant gene that contains a recognition site within its sequence is used to identify the bacteria that have successfully incorporated a recombinant plasmid. (When treated with the corresponding antibiotic, these bacteria will be affected, as the gene coding for antibiotic resistance has been cut, so will not be expressed). (1)

Question 51

Explain how the universality of the genetic code allows for the genetic modification of the rice embryos to produce Golden Rice.

(1 Mark)

Answer 51

• Because the genetic code is universal (i.e. the same codon will code for the same amino acid regardless of the organism), it allows for the gene of one organism, in this case, the Psy gene from daffodils to be expressed in another organism, the rice (1)

Question 52

Briefly describe the role of Rubisco in synthesising glucose in photosynthesis and outline how coenzymes are involved in this process.

(2 Marks)

Answer 52

• Rubisco fixes the carbon (from CO2) to make glucose (1)
• Coenzymes (ATP and NADPH) from the light-dependent stage provide the energy and hydrogen atoms needed to do this (1)

Question 53

Compare the process of photosynthesis in C4 and CAM plants.

(3 Marks)

Answer 53

• In CAM plants, initial carbon fixation is separated from the rest of the Calvin cycle over time while in C4 plants, initial carbon fixation is separated over space (different cells) (1)
• CAM plants open their stomata at night allowing CO2 to enter and close their stomata during the day to prevent water loss while C4 plants have their stomata open during the day (1)
• In C4 plants, initial carbon fixation occurs in mesophyll cell and the rest occurs in bundle-sheath cells while only mesophyll cells are involved in CAM plants (1)

NOTE: Must use COMPARATIVE statements. Do not simply outline the processes in each plant type.

Question 54

In prokaryotic cells, the DNA is not located in a nucleus. Explain why this allows for attenuation to occur in prokaryotic cells.

(1 Mark)

Answer 54

• Attenuation is made possible in prokaryotes because transcription and translation take place very close to each other in the cytoplasm, as the two processes are not separated by a nuclear membrane. (1)

Question 55

A new treatment for some cancers includes the use of conjugated monoclonal antibodies, which have anti-cancer drug attached.

The main advantage of using monoclonal antibodies in this new cancer treatment is that they…

(MC)

Answer 55

• Reduce the effects of the anti-cancer drug on non-cancerous cells

NOTE: Conjugated antibodies are antibodies that have a molecule attached which can be used to create a detectable signal.

Question 56

Rahul had been exposed to a strain of influenza in 2022 and was unwell for about a week until he fully recovered. When asked the following year if he intended to have an influenza vaccine, he declined as he said he already had memory cells.

Explain why Rahul may still be susceptible to the influenza virus in 2023, despite memory cells continuing to circulate in his body.

(4 Marks)

Answer 56

• Antigenic shift has occurred (1)
• The surface antigens have changed (1)
• Memory cells are no longer complementary (1)
• He has to undergo clonal selection and expansion again (1)

Question 57

It was suggested that herd immunity may help to reduce the spread of Lyme disease in the population. Do you agree or disagree with this suggestion? Justify your response.

(2 Marks)

Answer 57

• Herd immunity is effective for contagious diseases (1)
• Lyme disease is spread via ticks, not between human hosts (1)

Question 58

An individual infected with Lyme disease was given a course of antibiotics. They felt better after a few days so decided to stop taking the tablets and keep them in case of reinfection. What
potential consequence does this have for the individual and the bacterium?

(3 Marks)

Answer 58

• If any bacteria remain, they will replicate and make the person sick again (1)
• The bacteria that are not killed by the antibiotics may mutate (1)
• This creates a strain of bacteria that is resistant to the existing treatment (1)